Preparation and characterization of laser-melted Mg-Sn-Zn alloys for biomedical application

The rapid degradation rate of Magnesium (Mg) alloy limits its biomedical application even though it possesses outstanding biological performance and biomechanical compatibility. In this study, a combined method of laser rapid melting and alloying Zinc (Zn) was proposed to decrease the degradation rate of Mg-Sn alloy. The microstructure, degradation behaviors and mechanical properties of the laser-melted Mg-5Sn-xZn (x = 0, 2, 4, 6 and 8 wt.%) alloys were investigated. The results indicated that the grain size of the alloys decreased with increasing Zn content, due to the increased number of nucleation particles formed in the process of solidification. Moreover, the laser-melted Mg-Sn alloys possessed finer grains compared with traditional as-cast and as-rolled Mg-Sn alloys. The degradation rate of the alloys decreased with increasing Zn content (0-4 wt.%), which was ascribed to the grain refinement and the formation of Zn(OH)₂ protective layer. However, the degradation rate increased as the Zn content further increased (4-8 wt.%), which was caused by the galvanic corrosion between the Mg matrix and the generated Mg₇Zn₃ phase. Besides, Zn also increased the hardness of the alloys owing to the grain refinement strengthening and solid solution strengthening.